Current techniques for reducing the temperature drift of high frequency or microwave active devices are quite complex, utilize many applied components, and exhibit lengthy R&D periods, high cost, and high rate of failure. For example, the gain of high frequency or microwave power amplifiers, and thus their power output, varies with external temperature, seriously deteriorating the characteristics and stability of the amplifiers and even of the entire systems. To reduce the variance in the gain and the power of high frequency or microwave power amplifiers resulting from the variance in environmental temperature, many active devices, such as temperature detectors, power couplers, wave detectors, programmable signal processors, storage, and preamplifiers with automatic gain control (AGC) and automatic power control (APC) capabilities are included in the amplifiers themselves, their power sources and their control systems.
While resolving the temperature drift characteristics, several features of the devices must be satisfied:    (1) wideband characteristic;    (2) minimal refection coefficient for both the input and the output terminals;    (3) high isolation for both the input and the output terminals;    (4) the characteristic impedance of both the input and the output terminals complies with the requirement of the access system, for example, 50 Ohm or 75 Ohm.